Especially in endoscopic operations in the genitourinary tract the use of an irrigating fluid is required to gently dilate mucosal spaces and to remove blood and cut tissue from the operating field. There are several different irrigating fluids available commercially and the choice tends to be governed largely by tradition, although the price and properties of the fluid (e.g. stickiness and transparency) also play a role. The pharmacological effects of the fluid become important whenever it is absorbed by the patient. However, adverse reactions to irrigating fluids have not been documented as they have for drugs.
Most irrigating fluids were developed when the documentation of safety was much less important that it is today. Pharmacologists and regulatory authorities also pay little attention to solutions because they are conceived as devices (like soap and detergents) rather than drugs. Nevertheless, numerous reports of symptomatic and even fatal fluid absorption during TURP (transurethral resection of the prostate) and transcervical resection of the endometrium (TCRE, an operation for alleviating menorrhagia) emphasize the importance of using an irrigating fluid with a favourable profile of adverse effects.
For many years, little comparative data were available showing whether one irrigating fluid is more prone to adverse effects than others. However, during the past decade several studies covering this topic have been reported.
A summary of said reports and further details concerning irrigating fluids can be found in British Journal of Urology (1997), 79, 669–680. Some of said details will, however, be presented below.
Sterile water was used as irrigating fluid during the early years of TURP. However, obscure reactions with post-operative haemoglobulinuria sometimes occured and severe cases even led to death. Enrichment of the blood with salicylate and glucose when added to the sterile water made urologists realize, in 1947, that the absorption of the irrigating fluid into the circulation through severed prostatic veins must be the cause of the haemolysis. As electrolytes do not allow cutting by electrocautery, one or several non-electrolyte solutes capable of preventing haemolysis were then added to the irrigating fluid.
Glycine was the first suggested as suitable, and the other irrigating fluids used today, mannitol and mixtures of sorbitol and mannitol, were introduced somewhat later. An example of a document disclosing an irrigating fluid containing glycerine or mannitol is Journal of Surgical Research, Vol 95, 2001, pp 114–125. Reference can also be made to GB 2234897 A, which discloses the use of glycerine and L-arginine in an irrigating fluid.
Despite their non-haemolytic properties, absorption of the new irrigating fluids continued to be associated with adverse events which were often summarized as transurethral resection reactions (TUR syndrome). The clinical descriptions of this syndrome from the mid-1950s are still the cornerstones of our view of the risks associated with the use of irrigating fluids.
The uptake of small amounts of irrigating fluid occurs during almost every TURP and TCRE. The absorbed volume varies greatly and cannot be predicted in the individual patient, although it tends to be larger in extended and bloody operations. The uptake of 1 L of fluid, which corresponds to an acute decrease in the serum sodium concentration of 5–8 mmol/L, is the volume above which the risk of absorption-related symptoms is statistically increased.
Thus, in many cases the uptake of irrigating fluid, vascularly and extravascularly, is considerable. If said uptake exceeds 2–3 L the situation for the patient becomes lethal, and in more than 25% of actual cases the absorption has been reported to exceed 0.3 L.
Therefore, in addition to attempts to find an irrigating fluid composition which is absorbed to an extent as minor as possible, efforts have been made to find markers for such irrigating fluids by means of which absorbed amounts of fluid can be detected as early as possible.
One type of marker, or rather monitoring means, which is on the market, is a methodology where the patient is on a balance and his weight is checked. Such a methodology is, however, associated with considerable problems in calculating the amount fed to and removed from the patient during the course studied.
A different methodology is the use of ethanol as a marker added to the rinsing fluid. More specifically, ethanol is added to the fluid and the ethanol content of the air exhaled by the patient is recorded. The use of this new technique is disclosed in a number of documents, e.g. The Journal of Urology, Vol. 149, 502–506, March 1993, and U.S. Pat. No. 5,603,332. This method solved part of the problems but new problems arose instead. Thus, for instance, the speed of detection of exhaled ethanol is slow, the accuracy of detection of small amounts of ethanol is low and side effects with respect to the patient occur, such as dizziness and even alcohol dependence.
Primarily as a consequence of the non-accuracy of the method referred to a solute, especially glycine, has been added to the rinsing fluid (generally sterile water) so as to enhance the viscosity thereof, to reduce the absorbed amount of fluid, as well as to prevent or inhibit the heamolytic action thereof. However, by such a measure the irrigating fluid becomes less clear and the visibility for the surgeon is-reduced, which is a considerable disadvantage as a clear and good sight for the surgeon is an essential prerequisite for surgery of the kind referred to.